This invention relates to fuel dispensing nozzles of the type used to dispense gasoline for automobiles and the like, and more particularly, to an improvement to such a nozzle assembly to a low dispensing of fuel only when the nozzle is inserted into the inlet of a tank or container and to shut-off dispensing of fuel when the nozzle is removed or when an overpressure condition is sensed within the container.
As is well-known, gasoline dispensing nozzles of the type found in most service stations employ a spout which is inserted into the inlet of the filler pipe of an automobile's fuel tank. The size of the spout, and, in particular, its diameter is smaller than the diameter of the filler pipe. As a result, when the gas cap was removed from the filler pipe and the spout end of the nozzle inserted, there was typically substantial clearance between the side of the spout and the filler pipe. As a consequence, fuel vapors were allowed to escape from the tank into the atmosphere. Because of environmental concerns, it is now a requirement in many locales that fuel dispensing nozzles be equipped so this does not occur. One way utilized to meet these requirements is to provide the nozzle with a flexible bellows assembly which fits over the spout. The bellows is circular in cross-section with a diameter corresponding to the outer diameter of the filler pipe. Now, when the nozzle is inserted into the pipe, the end of the bellows fits snugly against the mouth of the pipe so that the only opening for gasoline vapors to escape is through a vapor passage in the nozzle.
In addition to the above, it is also desirable to prevent dispensing of fuel through a nozzle unless the spout is inserted into the tank. This is done to prevent accidental spillage which not only releases fuel vapors into the atmosphere, but also creates a potentially dangerous fire hazard. The addition of bellows on the nozzle has complicated this problem, and various schemes have been employed to insure pumping occurs only at the proper time. See, for example, U.S. Pat. Nos. 4,031,930 and No. 4,016,910, which are assigned to the same assignee as the present application, as well as U.S. Pat. No. 4,133,355 and No. 4,130,148. While each of the various systems shown in these patents work for their intended purpose, there is still a need for a simple, reliable system which prevents dispensing of fuel through a nozzle unless it is inserted in the filler pipe of a fuel tank with the bellows properly sealing against escape of vapor to the atmosphere.